donnell



March 3, 1964 c. K. DONNELL 3,123,541

CONTINUOUS DISTILLATION ANALYZER Filed Nov. 1, 1960 2 Sheets-Sheet 1Fig. .3

Indicating Temperature Controller Feed l6 Sample In Cooling Liquid In I844 Condensate Residue Integrator and Recorder 25 Dlstilled) 40 I DropProducmg Drop counting; IL 0 f8: iirf 'z g Circuitry P W Remote CAR IINVENTOR.

L, CONARD K. DONNELL ATTORNEY March 3, 1964 c. K. DONNELL CONTINUOUSDISTILLATION ANALYZER 2 Sheets-Sheet 2 Filed NOV. 1, 1960 INVENTOR.CONARD K. DONNELL.

ATTORNEY United States Patent 3,123,541 CUNTINUGUS DISTILLATIGN ANALYZERConard K. Donnell, Springfield, Pa., assignor to Sun Oil Company,Philadelphia, Pa., a corporation of New Jersey Filed No 1, 1960, Ser.No. 66,593 4 Claims. (Cl. 202-160) This invention relates to acontinuous distillation analyzer.

In the refining of petroleum, gas oils which are to be charged tocatalytic cracking units should contain a minimum ofgasoline-boiling-range material. This is because such a relativelylow-boiling traction passes through the cracking unit essentiallyunchanged, and remains in the catalytic gasoline as low-octanecomponent, depressing the octane rating of the catalytic gasoline.

According to prior practice, the amount of gasoline (low-boilingfraction) in the gas oil charge was determined by means of a batchdistillation procedure, using a long-neck distilling flask containingjack-chain packing. The aforementioned procedure was carried out inaccordance with Method 13-285 of the American Society for TestingMaterials (ASTM). The distilling flask referred to is called a Hempelflask, and the distillation procedure has become known as the Hempeldistillation. Usually, the volume percent of the charge distilled at 410F. and 440 F. vapor temperature is reported.

As previously stated, the conventional Hempel distillation is carriedout in batch-wise fashion, in the laboratory. Such batch-wise operationin the laboratory involves considerable delay in the obtaining andreporting of results, which is quite undesirable, and in additionrequires manual handling and transporting of samples, which can becomerather laborious.

Another type of distillation procedure which is quite common is theso-called Engler or ASTM distillation. In this procedure, thetemperature at which a certain percentage (e.g., 50%, 70%, 90%, etc.)ofthe charge has boiled oil or gone overhead is determined, and theresults are reported in temperature values, usually for the 10%, 50% and90% points of the charge. Here again, prior practice dictated batch-wisedistillation, in the laboratory.

An object of this invention is to provide a novel distillation anayzer,usable for either Hempel distillations or Engler distillations.

Another object is to provide a Hempel-type distillation analyzer whichoperates continuously and automatically, to give a continuous record ofthe percent of sample distilled at 440 F., or at any other desired,predetermined temperature.

The objects of this invention are accomplished, briefly, in thefollowing manner. Two spaced concentric tubes are arranged to serve as acombined distillation vessel and condenser. The inner tube is heated toan elevated temperature, while the outer tube is provided with a jacketthrough which a cooling fluid (e.g., air or water) fiows. The inner tubemay therefore be thought of as an evaporator, while the outer tube maybe thought of as a condenser. The sample to be analyzed is continuouslyfiowed at a known and constant rate onto the outer surface of the innertube, so as to flow downwardly therealong. A portion of the charge orsample vaporizes at the temperature of the inner tube, and travels asvapor to the outer, cooler tube, upon the inner Wall of which itcondenses. It then flows downwardly as condensate. For a Hempeldistillation, the drops of condensate or distillate are counted, as bymeans of a capacitance-type drop counter. In this way, the rate ofproduction of condensate is measured or determined. The residue,

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which remains unevaporated at the elevated temperature of the innertube, flows downwardly along the inner tube, and is abstracted from thebottom of the apparatus. Since the rate of feed to the vessel is knownand preset, and since for a Hempel distillation the rate of condensateor distillate production at the elevated temperature of the evaporatoris measured by counting and integrating the drops, the percent of thecharge which is distilled at the said elevated temperature can readilybe calculated. For an Engler-type distillation, the temperature of theinner tube is controlled so as to maintain a substantially constant droprate through the drop counter aforementioned (thus maintaining a fixedand known percent overhead, since the feed rate is known), and thetemperature of the inner tube is measured.

A detailed description of the invention follows, taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a schematic representation, partly in longitudinalcross-section, of a continuous distillation analyzer according to thisinvention;

FIG. 2 is a longitudinal, vertical cross-section through the dropproducing and sensing unit utilized in the invention;

FIG. 3 is a transverse cross-section taken along line 3-3 in FIG. 2; and

FIG. 4 is a vertical cross-section taken along line i -4 in FIG. 2.

Reference is now made to the drawings, and first to FIG. 1 thereof. Ahollow outer tube 1, made for example of glass, is provided with ajacket 2 through which a cooling fluid (erg, air or water) iscirculated, by means of the hose nipples 3 and 4 provided at the upperand lower ends, respectively, of the jacket 2. An inner hollow tube 5 ismounted and supported concentrically Within the outer tube 1, forexample by means of a flange 6 secured to the upper end of tube 5 andresting on the top of tube 1. Tube 5 is made from some material that isa good conductor of heat, such as nickel-plated copper. The tube 5 mayin some cases comprise two separate sections 5a and 5b rigidly fastenedtogether, end-to-end, the upper section 5a being a thin-walled tube andthe lower section 512 being a solid cylinder in which there is provideda longitudinal bore whose length is almost equal to the length of thecylinder. The common longitudinal axis of tubes 1 and 5 is vertical, sothat the tubes 1 and 5 are vertical, as illustrated in FIG. 1.

For convenience, the analyzer of this invention will be described firstas used for a Hempel-type distillation. Thereafter, there will bedescribed the use of the same analyzer (of the invention) for anEngler-type distillation.

A cartridge-type heater 7 is positioned within the bore in the lowertube section 5b, the electrical leads to this heater being indicated at8. Heater 7 functions, as will be described later, to heat tube 5 to asubstantially fixed predetermined (elevated) temperature. The lower endof tube section 51) is made of frusto-conical shape, as illustrated inFIG. 1, and is counterbored from its lower end to receive a thermocouple9 to'which are connected a pair of electrical leads 10. Leads 10 extenddownwardly through a drain tube 11, to be later described, to the bottomof the analyzer, and thence out through a cap 12 to an indicatingtemperature conroller 13. A suiable liquidtight seal is provided in cap12 around leads 10, to prevent any leakage of fluid through cap 12. Cap12 is provided with external threads, whereby a suitable electricalconduit may be coupled thereto. Temperature controller 13 may be of thepyrometer type, including a milliammeter to measure the output ofthermocouple 9, and this controller is supplied at 14 with alternatingcurrent power for heater energization purposes. The heater leads 8extend up through body section 5a and are connected to the output orcontrolled side of controller 13, Controller 13 is actuated from thethermocouple 9 (which is responsive to the temperature of tube 5), andthis controller operates to control (by means of an on-oil signal) theenergization of heater '7 (which is inside the lower end of tube 5) soas to maintain the temperature of tube 5 substantially constant. Thetemperature of tube 5 is maintained substantially constant at apredetermined temperature, e.g., 405 F.

The inner diameter of flange 6 is, for a substantial portion of theaxial length of this flange, made somewhat larger than the outerdiameter of upper tube section 50, thereby to provide an annular space15 at the upper end of tube 5. At its upper end, space 15 (whose lowerend is open) communicates with the inner end of a radiallyextendingconduit or coupling 16. Th outer end of coupling 16 is connected to thedischarge side of a feed pump 17, which operates to continuously pumpthe sample to be analyzed, at a known and constant rate, into coupling16 and through the latter to the upper end of annular space 15. pumpedto the top of annular space 15', from whence it flows downward over theouter surface of vertical tube 5 in a thin film, since the lower end ofannular space 15 is open. Pump 17 may be a gear pump, of the type knownas a metering pump.

In order to distribute the flow around the entire periphcry of tube 5 inthe form of a thin film, it has been found necessary to in eifectprovide a modification of the outer surface of tube 5, from a smoothcylindrical surface. Otherwise, the flow would take place only in two orthree narrow streams, over only a small portion of the periphery of tube5. One expedient which has been found effective to distribute the flowmore evenly is to first wind a piece of still wire tightly around ahexagonal mandrel, then remove the mandrel and place this same wire (inspiral form) rather tightly around the outside of tube 5, so as to coversubstantially the entire length of this tube. Due to its having beenwound around a hexagonal mandrel, the wire does not continuously contactthe cylindrical outer surface of tube 5, so that at the corners of thehexagon the wire is spaced from the outer surface of tube 5. This leavessufficient room for the liquid to flow rather freely over the outersurface of tube 5, yet the wire distributes the flow around the entireperiphery of such tube. The expedient just described has not beenillustrated in FIG. 1, as it is felt that to do so would undulycomplicate the drawings.

The open upper end of a small-diameter drain tube 11 is located somewhatbelow the lower frusto-conical end of tube section 512. The thermocoupleleads pass down through the length of tube 11, as previously described.The lower end of tube 11 is welded through a disk-like flange 18 whichseals off the bottom end of tube 1. A cap 19 is fastened near the lowerend of tube 11, this cap extending transversely to the axis of tube 11and having a bore extending entirely therethrough; the inner end of theaforesaid bore communicates with the tube 11. Cap 19 is provided withexternal pipe threads, whereby a drain pipe may be coupled thereto.

At its bottom end, tube 1 has a standard (tapered) pipe flange 26. Thelower end of tube 1 engages a gasket 21 which is positioned in anannular gasket recess provided in the upper face of the lower flange 18.Just inside of the inner diameter of recess 21, and radially outwardlybeyond tube 11, a piece 22 of stainless steel tubing is welded entirelythrough the lower flange 18, this piece of tubing extending downwardlyfrom flange 18 at a small inclination (say 10) outwardly from thevertical, and the upper end of this tubing terminating more or lessflush with the upper surface of flange 18. In order to seal the lowerend of outer tube 1 against leakage around its periphery, an upperflange 23 is utilized. Flange 23 has therein a central tapered aperturewhose taper matches that at 2%. Flange 23 is provided with a set of sixevenly- In this way, feed or sample (i.e., liquid charge) is ,isasaispaced tapped holes which extend through the thickness dimension of theflange and which match respective drilled holes extending through thethickness dimension of flange 13. Screws 24 extend freely through theholes in flange 18 and thread into the tapped holes in flange 23. Bytightening screws 24, flange 23 is urged downwardly toward flange 18,thus bringing the lower end of tube 1 into sealing engagement with thegasket in recess 21.

Since inner tube 5 is heated, it may be termed an evaporator. Sinceouter tube 1 is water-cooled (by means of jacket 2), it may be thoughtof as a condenser. The tubes 1 and 5 together form a distillationvessel.

These components or fractions of the charge supplied at to (which chargeflows downward in a thin film over the outer surface of tube 5, aspreviously described) which boil at or below the temperature of theheated tube or zon 5 are vaporized or boiled off from the inner tube.These travel as vapor to the second or cooled zone (water-cooled tube31), and are condensed on the inner surface of tube 1. This condensateor distillate flows downwardly along the surface of tube 1 to the bottomof the analyzer, and thence outwardly through tubing 22.

The undistilled residue (to wit, that portion of the charge which boilsabove the temperature of tube 5, and hence is not distilled in theanalyzer) runs down over the low-er frusto-conical or thermocouple endof tube 5 and thence down into drain tube ill, from whence it emergesfrom the analyzer by way of drain fitting 1?. Thus, it may be seen thatelements 11, 1% comprise a means for abstracting from the analyzer (ordistillation vessel ll, 5) that portion of the liquid charge which boilsabove the (predetermined) temperature of tube 5.

Since the feed rate is maintained constant by pump 17, the rate ofdistillate or condensate flow (through tubing .--.2) is a direct measureof the percent distilled at the predetermined temperature (thetemperature of tube 5, say 405 F). Thus, by measuring the flow rate ofthe condensate or distillate, the percent distilled at a temperature maybe readily determined.

The flow rate of a liquid stream can be measured conveniently, in thelow flow rate ranges below about ten cc. per minute, by counting dropsfalling from an orifice. By properly designing the orifice, the size ofthe drops can be maintained constant over a considerable range of flowrates.

The drops can be counted automatically, the usual detector being a lampand photocell arranged so that each drop interrupts the light beammomentarily, and produces a pulse output from the photocell. However,such an arrangement as this requires careful alignment of the lamp andphotocell with respect to the falling drops, so that each drop actuallyinterrupts the beam sufiiciently to be detected. Failure of the lamp, ofcourse, inactivates the system, and aging of components can aflcct itssensitivity enough to render it inoperative.

According to this invention, a capacitance system is used to countfalling drops of liquid, as a means of measuring flow rates. Accordingto this feature of the invention, the liquid condensate flowing intubing 22 is first formed into drops, and the drops are caused to passbetween the vertical plates of a small parallel-plate condenser whoseplates are sufliciently close together so that a single drop momentarilyfills a major fraction of the space between the plates. The liquid,acting as a diflerent dielectric (i.e., different from air) for thecondenser, alters the capacitance thereof sufficiently to be detectedreadily. The condenser plates are arranged so that each drop flows clearof the plates rapidly, with the result that the capacitance returns toits normal (lower) value before the next succeeding drop falls. Thepulses resulting from the individual drops are integrated to give a DC.voltage proportional to the drop rate, which voltage is recorded.

The condensed distillate issuing from tubing 22 flows as at 25 through adrop producing and sensing unit 26,

which in conjunction with a remote capacity unit 27 and drop countingcircuitry 28 produces an electrical pulse for each drop issuing from thedrop producing portion of unit 26. The constructional details of unit 26will now be described, with reference to FIGS. 2-4.

The drop producing and sensing unit components are all contained orsupported in a tubular housing 29 of insulating material. A dripper 30,designed to produce drops of a uniform size, is mounted with a slidingfit in the upper end of housing 29. Dripper 36% has an intermediatecylindrical body portion 30a of a diameter such as to fit within housing29, and an upper body portion 30b of larger diameter, the junctionbetween body portions 30a and 30b forming a shoulder 31 which rests onthe upper end of the hollow cylindrical housing 29. Dripper 30 has aninternal funnel-like liquid passage therein, comprising an upperinverted frusto-conical surface 32 the lower (and smaller-diameter) endof which opens into a longitudinal bore 33 which extends verticallydownwardly from the lower end of surface 32 Below the lower end ofintermediate body portion 30a, there is a lower cylindrical body portion3tic whose diameter is much smaller than that of body portion 390. Bore33 extends down into body portion 30c, and is bottomed at the lower endof body portion 30c. It is desired to be pointed out that, although bodyportion 3&0 has been described as a lower body portion, actually thedripper body extends below portion 36c (as will later become apparent),and bore 33 terminates above the extreme lower end of the dripper body.

At the lower end of bore 33, four holes 34 spaced 90 apart are drilledfrom the outside of the dripper body portion 301: into communicationwith bore 33. The axes of holes 34 extend at right angles to the axis ofbore 33, that is, the axes of these holes are horizontal. Below bodyportion 300, the dripper body is flared outwardly (by means of afrusto-conical section 319d) to a cylindrical terminal body portion 3%whose diameter is about 1 /2 times the diameter of body portion 360. Thelower face of body portion c (and also of the body 30) has a sharp edgeand constitutes a fiat horizontal bottom surface which is circular inshape.

As previously stated, the elements 3a3e and 3134 comprise a dripper. Theliquid condensate 25 emerging from the open end of tubing 22 (seeFIG. 1) is guided by surface 32 into bore 33, the liquid then flowingdown this bore and emerging from the lower end thereof by way of holes34. The dripper 30 is shaped to produce drops of a uniform size. Theliquid emerging from holes 34 flows downwardly over the outer surface ofbody section 360', and the drop forms on the flat horizontal bottomsurface of body section 3%, from which it drips downwardly toward thebottom of housing 29.

Adjacent the terminal body portion 30e, a pair of inspection holes 35(located 180 apart around the housing 29) are drilled through the wallof housing 29.

The parallel-plate condenser previously referred to is mounted inhousing 29, in such a position that the drops of condensate produced bydripper 30 can pass downwardly between the condenser plates. Twovertically disposed metal plates 36, each having an area of about /2 in.x /2 in. and a thickness of A in., comprise the parallel plates of thecapacitor or condenser which is used for sensing the drops ofcondensate. The plates are separated by an air gap 37 of to A in.; byway of example, this gap may be 20 mils (0202. in.) in thickness. Theupper end of each plate 36 is downwardly beveled as at 38, to guide thedrops into the gap 37 between the plates.

Although it is not illustrated in the drawings, the plates 36 may eachhe provided with a coating of insulating material (such as thetetrafluoroethylene material known as Tefion). This prevents sh'ontcircuitin-g of the plates by drops of water which may be present in thecondensate. If no water is expected to be present in the con- 3dens-ate, it would be preferable to omit this insulating coating fromplates 36, leaving these plates bare.

The plates 36 are supported each in a respective one of the twoinsulating spacers 39, which are substantially semicircular inhorizontal cross-section and the length of which exceeds that of theplates 36. Each of the spacers a recess cut therein into which therespective plate 36 fits, the recesses being rectangular in horizontalcrosssection and having arouate bottoms (see FIG. 4), the plates 36 alsohaving arcuatte boto-ms. The juxtaposed faces of the spacers 39 areseparated throughout their lengths by a gap which is commensurate withgap 37; thus, there is a gap which extends diametrically entirely acrosshousing 29 (see FIG. 3), and there is a gap which extends throughout thelengths of the spacers 39 (see FIG. 2).

Beginning at a plane below the lower (arcuate) ends of the plates 36,each of the spacers is formed with an inverted semi-conical surface;when in assembled position, these surfaces of the two spacers combine ineffect to provide a conical surface whose tip or apex is locatedconsiderably below the lower ends of the plates.

It will be recalled that, in effect, the gap 37 between the platescontinues uniformly (below the lower ends of the plates) down betweenthe insulating spacers 39, to the tip or apex of the cone formed 'by thetwo insulating spacers. Thus, in effect, the lower ends of the plates 36are extended with insulating material, so that the drops can flowsmoothly through the plates 36, and clear them before the next dropfalls. After reaching the apex or tip of the (inverted) cone formed byspacers 39, the drops continue downwardly and out the lower open end ofhousing 29.

In order to maintain the parts 36 and 39 in assembled position withinhousing 29, two screws 40 are utilized. Each of the screws 49 isessentially perpendicular to the length of gap 37, and each extendsthrough respective aligned holes drilled through housing 29 and arespective spacer 39 and threads into a tapped hole in a respective oneof the plates 36. Thus, the plates 36 and spacers 39 are maintained intheir proper positions in housing 29. At the same time, the screws 40provide a means for making a separate electrical connection to eachrespective metal plate 36. These connections may be made by wires 41(see FIG. 1) connected each to a respective screw 40.

A condenser or capacitor with the dimensions set forth has acapacitance, with dielectric, of 1 to 2 micrornicrofarads. Drops ofhydrocarbon liquid (condensate or distillate) between the platesapproximately double this capacitance, since the dielectric constant ofthe hydrocarbon is approximately twice that of This capacitancedifference, or change, is adequate to give reliable operation of acapacitance detecting circuit.

The leads 41 from the parallel plates. 36 are intended to be short, andextend to a remote capacity unit 27, from which a line 42 (which may belong) extends to the input of drop counting circuitry 28. The remoteunit 27 matches the high impedance of the sensing or measuring device tothe low impedance of the line 42. From the output of the countingcircuitry 28, a connection 43 extends to the input of'an inte'grator andrecorder 44. The units 27, 28, and 44 form no part of the presentinvention, so will'not be described in detail herein. For a morecomplete description of these units, reference may be had to thecopending Bachofer application, Serial No. 68,712, filed November 14,1960. For the present, suifice it to say that the drop countingcircuitry 28 functions to produce an output pulse corresponding to eachdrop passing between the plates 36. These pulses are rectified andintegrated by unit 44 to provide a DC. voltage proportional to the droprate, or rate of flow of distillate (condensate). This latter voltage isrecorded in unit 44 to provide a record of the distillate flow rate inthe analyzer of FIG. 1. Since the feed rate or charge rate (at 17) isknown and is maintained constant, the distillate rate is a directmeasure of the percent distilled at the (predetermined) temperature oftube 5.

The temperature at which the evaporator tube is operated, in thecontinuous analyzer of this invention, must be chosen by experiment.Because the distillation vessel disclosed herein is fundamentallydifferent from the ordinary Hempel flask, the degree of fractionation isdillerent. At equivalent temperatures, more distillate is produced inthe continuous analyzer than in the batch Hempel flask. Therefore, toobtain the same percentage distillate, the evaporator temperature mustbe lower in the continuous analyzer. For example, in one typicalapplication of the continuous analyzer of this invention, the evaporatortube 5 is operated at 405 F., in order to obtain the best correlationwith batch (conventional-type) results at 440 F. This is the reason forthe previous references to 405 F., in the above detailed description ofthe continuous analyzer of this invention.

Furthermore, even under these conditions there is not a oneat-o-onecorrelation between the continuous and batch distillations. By way ofexplanation, a sample that results in 2.5% distilled at 440 F. (batch orlaboratory distillation) will result in 2.5% distilled at 405 F.(continuous distillation, using the apparatus of this invention).However, if the distillate percentage (by batch distillation) decreasesto zero, the continuous analyzer will still show 1% distillate; if thedistillate percentage (by batch distillation) increases to 6%, thecontinuous analyzer will show only about 4%. But, this lack of aone-to-one correlation between the continuous and batch methods has noeffect on the actual operation of the continuous analyzer of the intendon, and at any rate can be overcome if necessary by applyingsuitable correction factors to the results obtained with the continuousanalyzer.

The capacitance-type drop counter described herein is particularlyuseful at rates of 1 to 10 drops per second past the condenser plates.

As previously stated, the preceding description has referred to the useof the analyzer of the invention for a Hempel-type distillation, whereinthe temperature of tube 5' is mm'ntained at a substantially fixed,predetermined value, and wherein the percent distilled (percentoverhead) at this temperature is measured by means of thecapacitance-type drop counter described. However, the analyzer isequally applicable to so-called Engler-type distillations. For suchdistillations, heater 7, instead of being controlled by thetemperature-responsive controller 113, is controlled by the output ofthe drop counting circuitry 28. The control of the heater is made tooccur in such a way as to maintain the drop rate through the sensingunit 26 substantially constant, and at a predetermined value; this wouldcorrespond, of course, to a fixed percentage overhead (such as 50% or95%), since the feed rate to the analyzer is known and constant. Typicalcircuitry for such control of the heater is disclosed inthe'above-mentioned Bachofer application. In this type of distillation,the temperature of tube 5 (which then corresponds to the temperature atwhich a certain known percentage of the charge goes overhead) ismeasured, as by means of thermocouple 9.

In some instances of the application of the analyzer to Engler-typedeterminations, the drop producing and sensing unit 26 may be coupled todrain tube 11, so as to sense the residue (rather than being coupled totubing 22, so as to sense the condensate). Such sensing of the residuemay be particularly advantageous when the 95 point of the charge isbeing determined, since then the 95% overhead may involve too high arate of flow through tubing 221501 proper operation of thecapacitancetype drop counter described; on the other hand, the 5%residue involves a flow rate which is appropriate for the drop counter.

The invention claimed is:

1. A continuous distillation analyzer comprising a hollow outer tubeprovided with a jacket; means for circulating a cooling liquid throughsaid jacket, an inner tube mounted concentrically within said outertube, controllable means for heating said inner tube, means responsiveto the temperature of said inner tube for controlling said controllablemeans to maintain said inner tube at a substantially constant elevatedtemperature, means for continuously flowing, at a known rate, a liquidto be analyzed onto the outer surface of said inner tube, and means fordetermining the rate of production of all of the liquid which is boiledoff from said inner tube and collects as condensate on said outer tube.

2. A distillate analyzer as defined in claim 1, wherein the determiningmeans includes a parallel-plate capacitor arranged so that thecondensate is received between its plates, as a dielectric.

3. A continuous distillation analyzer comprising a hollow outer tubeprovided with a jacket; means for circulating a cooling liquid throughsaid jacket, an inner tube mounted concentrically within said outertube, controllable means for heating said inner tube, means responsiveto the temperature of said inner tube for controlling said controllablemeans to maintain said inner tube at a substantially constant elevatedtemperature, means for continuously flowing, at a known rate, a liquidto be analyzed onto the outer surface of said inner tube, means fordetermining the rate of production of all of the liquid which is boiledoff from said inner tube and collects as condensate on said outer tube,and means adjacent one end of said inner tube or continuouslyabstracting that portion of the analyzed liquid which is not boiled offfrom said inner tube.

4. A distillation analyzer as defined in claim 3, wherein thedetermining means includes a parallel-plate capacitor arranged so thatthe condensate draining oil said outer tube is received between theplates of the capacitor, as a dielectric.

References titted in the file of this patent UNITED STATES PATENTS1,845,159 Lea Feb. 16, 1932 2,117,802 Hickman May 17, 1938 2,180,052Hickman et a1. Nov. 14, 1939 2,240,618 Harris Mar. 6, 1941 2,363,247Holder NOV. 21, 1944 2,392,893 Williamson Jan. 15, 1946 2,450,098 SmithSept. 28, 1948' 2,530,376 Castle et a1. Nov. 21, 1950 2,577,615 Garrisonet al. Dec. 4, 1951 2,595,948 Jones May 6, 1952 2,615,706 Davey Oct. 28,1952 2,616,839 Arnes Nov. 4, 1952 2,650,085 Burnett Aug. 25, 19532,772,393 Davis Nov. 27, 1956 2,785,374- Fay et al. Mar. 12, 19573,009,364 Webb NOV. 21, 1961 OTHER REFERENCES Instruments and ProcessControl, published by NY. State Vocational and Practical ArtsAssociation, 1945, pp. -185.

American Journal of Clinical Patholog vol. 26, No. 12, December 1956,pp. 1439-1449.

1. A CONTINUOUS DISTILLATION ANALYZER COMPRISING A HOLLOW OUTER TUBEPROVIDED WITH A JACKET; MEANS FOR CIRCULATING A COOLING LIQUID THROUGHSAID JACKET, AN INNER TUBE MOUNTED CONCENTRICALLY WITHIN SAID OUTERTUBE, CONTROLLABLE MEANS FOR HEATING SAID INNER TUBE, MEANS RESPONSIVETO THE TEMPERATURE OF SAID INNER TUBE FOR CONTROLLING SAID CONTROLLABLEMEANS TO MAINTAIN SID INNER TUBE AT A SUBSTANTIALLY CONSTANT ELEVATEDTEMPERATURE, MEANS FOR CONTINUOUSLY FLOWING, AT A KNOWN RATE, A LIQUIDTO BE ANALYZED ONTO THE OUTE SURFACE OF SAID INNER TUBE, AND MEANS FORDETERMINING THE RATE OF PRODUCTION OF ALL OF THE LIQUID WHICH IS BOILEDOFF FROM SAID INNER TUBE AND COLLECTS AS CONDENSATE ON SAID OUTER TUBE.